1. Technical Field
The present invention relates to a test apparatus.
2. Related Art
A known switching device used in a large-current circuit is a device that uses an element such as an insulated-gate bipolar transistor (referred to hereinafter as an IGBT). In such a device, a plurality of IGBT elements are arranged in parallel according to the desired current specifications, as shown in Patent Document 1, for example. A test apparatus that tests this device supplies power from a common power supply to the IGBTs.    Patent Document 1: Japanese Patent Application Publication No. 2000-58820
One type of test for a large-current switching device is an avalanche breakdown test. In an avalanche breakdown test, the device under test is connected to an inductive load, such as an inductor, and electrical energy is accumulated in the inductive load while the device under test is in a conductive state. After this, the device under test is switched to a non-conductive state and the electrical energy accumulated in the inductive load is applied to the device under test, thereby testing the tolerance of the device under test.
The current flowing through the device under test as a result of a voltage exceeding the rated value of the device under test being applied thereto while the device under test is in a non-conductive state is referred to as the “avalanche current.” The period during which the avalanche current flows is referred to as the “avalanche period.” The voltage applied to the device under test during the avalanche period is referred to as the “avalanche voltage.”
When the device under test malfunctions in a short circuit mode during the avalanche period, an excessive current flows through the device under test. When an excessive current flows through the device under test, damage spreads in the device under test and it becomes difficult to analyze the cause of the malfunction of the device under test. Furthermore, the excessive current can damage the test apparatus. In order to prevent damage to the device under test and the test apparatus, it is very important that, when the device under test malfunctions, the current from the inductive load be quickly prevented from flowing through the device under test by using a switch, for example.